Control means for regulating the output of x-ray apparatus



April 21, 1959 E. v. REED ETAL I 2,883,554

CONTRQL MEANS FOR REGULATING THE OUTPUT 0F X--RAY APPARATUS s sheets-sheet 1 Filed June 4, 1953 INVENTORS EARL v. REED a. HA 01.0 av Y Q1/- 1 v ATTOR EYS,

April 21, 1959 E V; REED 'El'AL 2,883,554

CONTROL MEANS FOR REGULATING THE OUTPUT OF X-RAY APPARATUS Filed June 4, 1953 V 3 Sheets-Sheet 3 INVENTORS EARL V. REED &

I BY'- WAEOLD B. 2/

' AT'II'OR EYIS.

United States Patent CONTROL MEANS FOR REGULATING THE OUTPUT OF X-RAY APPARATUS Earl V. Reed, Elmwood Park, and Harold B. Valley, Elmhurst, Ill., assignors, by mesne assignments, to Land- Air, Inc., a corporation of Illinois Application June 4, 1953, Serial No. 359,474 7 Claims. (Cl. 250-95) The presentinvention relates to X-ray apparatus and more particularly to novel control means for accurately regulating theoutputofsuch apparatus.

In setting up technique on an X-ray control it has heretofore been necessary to select the X-ray tube current and to select the lengthof time of the exposure as well as the proper kilovoltage. applied to the X-ray tube. One serious objection or inherent disadvantage of the above method or manner of setting technique is that it comprehends a manual operation and. is subject to errors both in the correct technique to be applied and in the permissible load applied to the X-ray tube anode.

The present invention obviates the above noted objections by providing novel control circuits for automatically regulating or controlling the output of such X-ray apparatus.

Itisa further important object of the present invention to provide a novel means and manner of automatically selecting a predetermined safe output load of the X-ray tube anode simultaneously with the selection of the desired product of milliamperes and seconds.

Another object is to adapt the present invention. to a timer employing a phototube timing circuit to regulate the total quantity of X-ray outputfrom an X-ray tube.

A still. further object is to adapt the present invention to a timer employing an ionizationchamber to measwe the X-ray output of the X-ray tube in quantitative terms.

In the drawings:

Figure 1 is a wiring diagram illustrating one form of control circuit embodied in the. present invention for regulating or controlling the output of X-ray apparatus.

Fig. 2' isa wiring diagram .of another illustrative embodiment of the present novel invention adapted to a phototube timing system.

Fig. 3 is. a wiring diagramv of a further illustrative embodimentof the control circuit'contemplated by the present invention but, adapted to a timer employing an ionization chamber to measure the X-ray output of the X ray tube in quantitative terms.

7 Referring more particularly to the disclosure in the drawings and to the novel illustrative embodiments therein selected, in Fig. 1 we have shown an auto transformer 11 supplied by a suitable source of electrical energy designated L1v and L2. Leads 12 and 13 connect the auto transformer 11 to the primary winding 15 of a high voltage transformer 15. The secondaries 15 and 15 of this transformer are connected by the leads 16 and 17, respectively, to an X-ray tube 18. The filaments 18 and 18 of this tube are connected'by leads 19 and 20, and by leads 20 and 21,-respectively, to the secondary windings 22 and 23 of filament transformers 22 and 23.

Primary windings 22 and 23 of filament transformers 22and 23, respectively, are connected to the auto transformer through a lead 25. A lead 26' connects the auto transformer 11 to a resistor 27 which is provided with a number of adjustable taps corresponding to the points or taps 28 28 28, 28 and 28 on switch 28 and points 2 or taps 29 29*, 29, 29 and 29 of the switch 29. The primary winding 22 of the filament transformer 22 is connected by means of lead 33 through a pole 32 of a filament selector switch 32 and through a milliampere selector switch 29 to the resistor 27, while the primary winding 23 of the filament transformer 23 is connected by a lead 34 through a pole 32 of the filament selector switch 32 and through a milliampere selector switch 28 to the resistor 27. This filament selector switch 32 is wired in such a manner that only one of the filament transformers 22 and 23 will be energized at any particular time.

The timing of the exposure is governed by a gas discharge tube 35 having an anode 35 a grid 35 and 'a cold cathode 35, with the supply voltage for this tube provided by a transformer 36 having its primary winding 36 connected to the autotransformer 11 by means of leads 25 and 26. A rectifier tube 37 is connected to the secondary winding 36*- of the transformer, 36 and to a filament winding 36 of the transformer 36 to supply rectified voltage to thegas discharge tube 35 by meansof leads 38 and 39. The grid 35* of the tube 35 is connected to a condenser 40 by means of a lead 42 and to a resistor 41 by means of a resistor 47 and a selector switch 30 having a plurality of points or taps 30 30*, 30, 50 and 30 connected to corresponding adjustable taps on resistor 41. The lead 39 provides the return path or circuit from the resistor 41 to the condenser 40. to the cathode 35. Resistor 41 is also connected to a secondary winding 15 of the high voltage transformer 15 by means of the lead 43.

The, exposure is started by depressing a switch 44 thereby applying voltage from the auto transformer 11 through the lead 25, through the switch 44, through the lead 45, through normally closed contacts 46 of a relay 46-to a relay 14 and through the lead 26 to a point of different potential on the auto transformer 11, thus energizing the relay 14 and closing the normally open contacts 14 Relay 14 thus being energized closes the circuit from the auto transformer 11 through a selector switch 47, through the lead 13, through the contact 14 to the primary 15 of the high voltage transformer 15, then,

' the lead 43 and through the resistor 41 to ground. A

voltage is thus developed across the resistor 41 in proportion to the X-ray tube anode current. A portion of the voltage developed across the resistor 41 by the X-ray tube current is connected through the timer selector switch 30, through the charging resistor 47 to the condenser 40 and by means of a lead 42 to the grid 35* of the tube 35 and thus charging the condenser 4%). Tube 35 tires when the condenser 40 charges up to its critical vane and thereby energizing the relay 46 and opening the contacts 46 whereby the relay 14. is deenergized andv the contacts 14 are opened to thereby terminate the exposure.

Since the voltage applied to the grid 35 of the trigger tube 35 is dependent on the charging of the condenser 40, the timing of the X-ray exposure will be proportional to the product of the tube current in milliamperes and time in seconds. Thus the timer selector switch 39 is calibrated in milliampere seconds rather than in units of time.

It is well known that X-ray tubes have definite heat storage capacities and heat dissipation rates, and that they. must not be loaded beyond their capacities or they will be damaged or destroyed. As an example, one particular X-ray tube is capable of operating at 100 peak kilovolts and 200 milliamperes for one second or a total of 200 milliampere seconds, while at 100 peak kilovolts and 125 milliamperes it is capable of operating for four seconds or a total of 500 milliampere seconds.

It is thus apparent that in the event the millampere second selector 30 were set for 400 milliampere seconds and the milliampere selector switch 29 were set for a tube current of 200 milliamperes and an exposure made at 100 peak kilovolts, an X-ray tube with the above mentioned ratings would be grossly overloaded.

In the present invention the milliampere second selector switch 30, the milliampere selector switch 29 and the milliampere selector switch 28 are all actuated and controlled by a common shaft 31 in such manner that for each selection of a milliampere second value there is a definite, corresponding selector point on the milliampere selector switches 28 and 29. Thus a predetermined safe value of the X-ray tube current may be set by means of the adjustable filament resistor 27 to automatically insure safe operation of the X-ray tube over the entire range of the milliampere second selections.

Fig. 2 is a modification of the discloseure of Fig. 1 but showing the present invention adapted to and embodied in a phototube timing circuit and in which corresponding elements and those functioning in a like manner to those of Fig. l have been given the same reference characters and only those new elements or parts and their functions will be herinafter described in detail.

In Fig. 2, X-rays from the X-ray tube 18 pass through a body 50, through a film 51 and through a fluorescent screen 52, thus producing an image of the body 50 on the film 51 and causing the fluorescent screen 52 to fiuoresce in proportion to the X-radiation of film 51. Light from the fluorescent screen 52 impinges on a cathode 53 of a phototube 53 causing electrons to be emitted in proportion to the light received and thus in proportion to the X-radiation on the film 51. Current then flows from the power supply through the lead 38 and through a portion of a resistor 54 having adjustable taps corresponding to the taps or points 3%, 30*, 30, 30 and 30' on the switch 30, through the switch 30, through a lead 55 to anode 53 and phototube 53 and through the lead 42, thus charging the condenser 40. As soon as the condenser 40 charges up to the critical voltage of the gas discharge tube 35, this trigger tube 35 will fire and terminate the X-ray exposure as described in Fig. l.

The sensitivity of the phototube 53 is adjusted by adjusting the applied voltage by means of the selector switch 30 and the resistor 54. t

In this embodiment of our invention we show the selector switch 39 connected to the milliampere selector switch 29 by means of a common actuating shaft 31 in such a manner that for any given phototube sensitivity setting on the selector switch 30 there is a corresponding point on the milliampere selector switch 29. Thus a predetermined safe value of X-ray tube current may be set or determined by means of the adjustable taps on the resistor 27 corresponding to the points or taps 29 29 29 29 and 29 on the switch 29 whereby to automatically insure safe operation of the X-ray tube over the entire range of phototube sensitivity settings for all normal conditions.

Fig. 3 is another modification of the disclosure of Fig. l but showing our invention adapted to a timer using an ionization chamber to measure the X-ray output of the X-ray tube in quantitative terms. As in Figs. 1 and 2, similar elements or parts and those functioning in a like manner to corresponding parts in Figs. 1 and 2, have been given the same reference characters and only those new or added elements or parts and their functions will be explained.

In Fig. 3, X-rays from the X-ray tube 13 pass through an ionization chamber 69, thus ionizing the atmosphere inside this chamber. Current flows from the power supply through the lead 38 to an element 60 and to an element 60* of the ionization chamber 60, and through the lead 42 4 to the selector switch 30 and tap condenser 40 The voltage on the condenser 40 appears on the grid 35 of the gas discharge tube35, so that the tube 35 fires when the voltage of the condenser 40 charges up to the critical value, thus terminating the X-ray exposure. The total quantity of X-ray energy emitted by the X-ray tube 18 can be adjusted and made smaller or larger by selecting condensers 40 40, 40* or 40 of smaller or larger capacity by means of the selector switch 30 and corresponding taps or points 30 30, 30 or 30 In this embodiment, We have shown the selector switch 30 connected to the milliampere selector switch 29 by cans of a common actuating shaft 31 in such manner that for any given setting of X-ray tube output on the selector switch 30 there is a corresponding point on the milliampere selector switch 29. Thus a predetermined safe value of X-ray tube current may be set by means of the adjustable taps on the resistor 27 corresponding to the points or taps 29 29', 29, 2S! and 29 on the switch 29 to automatically insure safe operation of the X-ray tube over the entire range of X-ray tube output.

In Figs. 1, 2 and 3, we have shown our invention adapted to a self-rectified, single X-ray tube X-ray system. However, our invention is not limited thereto and those skilled in the art will recognize that this invention is equally adapted to systems of the half wave rectified and full wave rectified types involving the use of one or more X-ray tubes.

Having thus disclosed the invention, we claim:

1. An X-ray apparatus including an X-ray tube, control means for controlling the rate of output of said X-ray tube at a predetermined rate and adjustable for altering the rates of said X-ray tube output, timer means for controlling the time of said X-ray tube operation including a resistor in series with the X-ray tube anode current to produce a voltage proportional to said X-ray tube anode current, a condenser for receiving charging current from said resistor, a trigger tube having a grid connected to said condenser and adjusted to fire at a predetermined critical voltage on said grid and -a plate and cathode, and a relay circuit means connected to said plate and cathode and sensitive to firing of said trigger tube for terminating the period of said X-ray tube operation, said timer means being adjustable for varying the amount of said X-ray tube output and connected to said control means in such manner as to simultaneously adjust the amount and rate of X-ray tube output.

2. An X-ray apparatus including an X-ray tube, adjustable control means for regulating the rate of output of the X-ray tube and adjustable to vary the rate of output, a resistor providing control means in series with the X-ray tube anode current for regulating the quantity of X-ray tube output and adjustable to vary such quantity, including a selector switch calibrated in terms of X-ray tube output, a condenser charged by the current through said resistor, circuit interrupting means for said X-ray tube controlled by said condenser, and means for connecting the output control means to said first mentioned control means whereby to automatically and simultaneously adjust the rate and quantity of X-ray tube output.

3. An X-ray apparatus including an X-ray tube, adjustable control means for regulating the rate of output of the X-ray tube and adjustable to vary the rate of output, an adjustable resistor providing timing means in series with the X-ray tube anode current for regulating the period of X-ray tube operation and adjustable to vary the value of the product of the X-ray tube anode current 30 to thus charge a and time of operation including a time selector switch,

calibrated in milliampere seconds, a condenser charged by the current through said resistor, circuit interrupting means for said X-ray tube controlled by said condenser, and means for connecting the timing means to said con trol means whereby to automatically and simultaneously adjust the rate of the X-ray tube output and the value of the product of the X-ray tube anode current and the time of operation.

4. In an X-ray apparatus including an X-ray tube, means for controlling the output of the X-ray tube at a desired rate, means for adjusting said control means whereby to alter the rate of output, and means for regulating the time of X-ray exposure and adjustable to vary the period of exposure, said time regulating means including a time selector switch calibrated in milliampere seconds, a resistor in series with the X-ray tube anode current, a condenser for receiving charging current from said resistor, a trigger tube with the voltage applied to the grid of said trigger tube being dependent on the charging of the condenser whereby the time of the X-ray exposure is proportional to the product of the tube current in milliamperes and time in seconds, and means under control of said trigger tube for interrupting operation of said X-ray tube when said trigger tube fires.

5. In an X-ray apparatus including an X-ray tube, means for controlling the output of the X-ray tube at a desired rate, means for adjusting said control means whereby to alter the rate of output, means for regulating the time of X-ray tube operation and adjustable to vary the period of said operation by varying the Value of the product of the X-ray tube anode current and the period of operation, said time regulating means including a time selector switch calibrated in rnilliampere seconds, a resistor in series with the X-ray tube anode current to produce a voltage proportional to said X-ray tube anode current, a condenser for receiving charging current from said resistor, a trigger tube having a grid connected to said condenser and adjusted to fire at a predetermined critical voltage on said grid, means for connecting the time regulating means to the control means for automatically selecting a predetermined safe output load of the X-ray tube anode simultaneously with the selection of the desired product of milliamperes and seconds, and means responsive to the firing of said trigger tube for interrupting operation of said X-ray tube.

6. An X-ray apparatus including an X-ray tube, control means for controlling the rate of output of said X-ray tube at a predetermined rate and adjustable for altering the rates of said X-ray tube output, timer means for controlling the time of said X-ray tube operation inciuding a fluorescent screen in the path of the X-radiation from said X-ray tube, a light sensitive phototube to receive light from said fluorescent screen, a condenser to receive charging current from said phototube, a trigger tube having a grid connected to said condenser and adjusted to fire at a predetermined critical voltage on said grid and a plate and cathode and a relay circuit means connected to said plate and cathode and sensitive to firing of said trigger tube for terminating the period of said X-ray tube operation, said timer means being adjustable for varying the amount of said X-ray tube output and connected to said control means in such manner as to simultaneously adjust the amount and rate of X-ray tube output.

7. An X-ray apparatus including an X-ray tube, control means for adjusting the rate of output of said X-ray tube at a predetermined rate and adjustable for varying the rate of X-ray tube output, an ionization chamber in the path of X-radiation from said X-ray tube for measuring the X-ray tube output, an electrical circuit and relay means sensitive to the output of said ionization chamber for terminating the X-ray tube output and adjustable for different amounts of X-ray tube output, said electrical circuit and relay means being connected to said control means in such manner as to simultaneously adjust the amount and rate of said X-ray tube output.

Weiglass July 18, 1944 Goldfield et a1. Oct. 23, 1951 

